Re: Static IP outside of router DHCP range



Smarty wrote:
"Mark" <i@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:jpljb5h5spkp8qmomu0h06afrhujc1hlna@xxxxxxxxxx

On Tue, 22 Sep 2009 23:23:20 -0400, "Smarty" <nobody@xxxxxxxxxx>
wrote:

"ohaya" <ohaya@xxxxxxx> wrote in message
news:3Pfum.135564$nL7.93077@xxxxxxxxxxxxxxx



david wrote:

On Tue, 22 Sep 2009 13:16:31 -0400, Smarty rearranged some electrons to
say:


"ohaya" <ohaya@xxxxxxx> wrote in message
news:n8Ctm.438292$Ta5.405120@xxxxxxxxxxxxxxx


Smarty wrote:

"Rarius" <rarius@xxxxxxxxxxxx> wrote in message
news:Xnutm.36702$nP6.2817@xxxxxxxxxxxxxxx


Smarty wrote:


Thanks to all for replies.

I would very much like to fix the assignments to MAC addresses,
since each of my 8 video clients has a label with the Mac address
printed on it, and all 8 clients remain located in exactly the same
network locations regardless of when I reboot. The fact that they
are, in most cases, connected to switches fed from the router causes
additional confusion when the video server IP changes, since the
switches appear to "keep" old routing information for a while and
sometimes require rebooting also.

I have looked over my Linksys settings pretty carefully but have yet
to find a method to put hard-wired Mac addresses into this Linksys
router. I may switch to another router if I can be certain that it
supports this feature and also has the ability to route to a couple
dozen devices reliably.

Thanks again for the help!



I cannot understand why you want to do anything with the MAC
addresses. As I understand it your 8 video clients are just that
"clients". Your router does not need to know about the clients and
neither does the server. The server PC is the only one that needs a
fixed IP address so the clients can find it.

As long as the 8 clients are all DHCPing their IP settings (address,
mask, etc) it doesn't matter WHICH address they get from the DHCP
server. Every address in the DHCP range will work fine for every
client machine.

The rule of thumb is... server = fixed IP, client = DHCP.

Rarius




The issue (apparently) is that loss of power / reboot, using a dynamic
IP for the video server, can and often does result in a new video
server IP address being assigned when the router / video server come
up. The 8 clients use BootP to upload a copy of their run-time (Linux)
application which contains the client GUI, mpeg2 decoder, etc. for
playback. They fail to find the boot server, now at a new address, and
are (apparently) not able to easily get themselves booted. I am hoping
that a fixed IP address for the video server, where the 8 clients get
their boot server uploads, will now be much less difficult and time
consuming.

I raised the entire matter of MAC addresses only because each of the 8
clients has a clearly labeled and unique hard-coded MAC address which
(if I had a way to create a map / table in my video server) could
route 'instantly' without the ambiguity of issuing new IP addresses
for both the video server and 8 clients every time a power glitch
occurs. It is my impression that 3 100BaseT Netgear switches I use in
my network also have some "memory" in their port multicasting logic /
look up table which "remembers" the prior IP addresses of the clients
attached to them, and thus becomes a temporary dead-end for packets
being routed to the new client IP addresses after DHCP assignments
occur following reboot. Unplugging the switches and plugging them in a
minute or two later seems to solve this problem, but there is a
temporary period where the switches don't seem to be forwarding
properly during the BootP process. Thus I brought up Mac addresses as
an alternative way to perhaps avoid the DHCP quagmire.

My apologies if the original post was incomplete, vague, or both. I am
going to try the recommended approach to fix the video server IP
address statically, now that I understand that the Linksys can route
to the entire range of addresses in the subnet, beyond the range I
have defined for automatic DHCP assignment. Perhaps this will be
enough of a solution.

Many thanks again.



Hi,

Ahhh... Ok, that's better... thanks for the explanation of what you're
actually trying to do.

So, are you saying that "your" server (the one for which you were
trying to set a fixed IP address) is also acting as a BOOTP server?

I haven't worked with this kind of stuff for awhile (use to work with
PXE/TFTP booting, etc., but years ago!), but, according to this:

http://en.wikipedia.org/wiki/Bootstrap_Protocol

"The Dynamic Host Configuration Protocol (DHCP) is a more advanced
protocol for the same purpose and has superseded the use of BOOTP. Most
DHCP servers also offer BOOTP support."

Do you know whether or not whatever is acting as the DHCP server on
your network (I'm assuming that router) is also acting as a BOOTP
server?

If it is, and if "your" server is also acting as a BOOTP server, maybe
that's part of your problem?

According to this:

http://www.eventhelix.com/RealtimeMantra/Networking/Bootp.pdf

the client sends a BOOTP_REQUEST using UDP, with a broadcast
(255.255.255.255) destination address.

[NOTE: If the clients are indeed sending the BOOTP_REQUESTs with UDP
and a broadcast address, then setting your server to a fixed IP address
is probably not what your problem is, since your server should see the
broadcast request regardless of its own IP address.]

So, if BOTH your router AND "your" server are acting as BOOTP servers,
maybe both of them are responding to the BOOTP_REQUEST?

It might be worthwhile to run a separate machine on the network, with a
sniffer (e.g., Wireshark) running, to see what is going on?

Jim



Jim,
I am very interested in your earlier comment about sniffers / Wireshark,
and wonder if you or others here may be aware of any very low cost or
freeware method to do some network analysis of traffic. I don't expect
much given my requirement to keep it cheap / low cost, but I would be
curious to see what tool or tools might be good for looking at traffic,
not necessarily using a dedicated / separate computer as the sniffer.
Any thoughts would be much appreciated.



google --> wireshark



Hi,

As david pointed out, Wireshark is free. I also occasionally use Nirsoft
SmartSniff:

http://www.nirsoft.net/utils/smsniff.html

which is also free, esp. when I don't want to, or can't install WinPcap on
a system.

Jim


Thanks to you and David for replies. I previously went to Google and found a
misleading website offering Wireshark on a trial basis for free, and then
offering a $499 purchase price. Had I done more investigating, as I did
tonight, I would have realized that Wireshark is what Ethereal is now
renamed, and that it is open source and free. I have used Ethereal a few
years ago, and had forgotten about it as a suitable tool for this type of
use. I'm going to have to play around with it again and see how it works.


If you install Wireshark on a different PC and you still use a switch
then you won't see most of the traffic because the switch will be only
sending packets to their destination.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking most articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.
[Reply-to address valid until it is spammed.]




Excellent point and thanks for the warning!



But you would see it if you were using a hub, instead of a switch :)...

Jim

.

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